An edit suite used in television production and post-production systems will typically contain a vision mixer, digital video effects unit (DVE) and edit controller. Additionally a routing switcher, color corrector and an assortment of other processing devices may well be made available.
Often each of these products will have been produced by different manufacturers. Although every attempt will have been made by these manufacturers to ensure conformity to industry standard protocols and interfaces, some non-conformity is inevitable in order to extract optimum performance and functionality from a particular device.
This non-conformity often causes problems for operators and engineers working with the system. An operator will have to learn the operating style of each individual device and the best way to communicate between devices. An engineer may have to address timing problems and interface protocols requiring a great deal of communication with individual manufacturers.
Several manufacturers have recognised the problem and have begun to produce products which are designed to work together.
FIG. 1 shows the traditional layout of a mixer and digital effects unit which is used in some recent units. In this figure a mixer 10 comprises a mix-effects device (M/E) 12 and a down stream key (DSK) 14. Primary inputs are taken into the mixer where they may be mixed, wiped or keyed together. A dedicated loop (usually only one) provides an exit and re-entry system allowing a primary source to be manipulated by the separate digital effects device (DVE) 16 and recombined within the mix-effects without any appreciable timing or communication difficulties. The output of the mix effects and/or pgm/pst bus is then put through the downstream key 14 which is the last section of processing in the chain and is generally used for the addition of captions or credits. This approach of FIG. 1 works well, however, it does introduce some constraints which have been accepted in the industry but which apply limitations. For example, signal processing through the system takes place in a very structured way.
The complexity of the system obviously depends on the particular choice of mixer and digital effects device combination. Some very powerful systems can deal with up to 10 layers of video in a single pass and may well command a price tag of around 250,000. However, very often even these very powerful systems will only be required to produce a composite of 4 or 5 layers. The extra functionality being required due to the inflexible architecture and timing problems inherent in such a system.
Such systems can be wasteful of circuitry, as a good deal of built in redundancy is required to overcome the inflexibility of this very structured architecture. Some installations have made these systems work extremely well with the aid of external matrixes and processing devices. However, those are in the minority.
The inflexibility of the prior art can be appreciated by considering a situation where a primary input was fed to M/E 12 and external key and external fill applied followed by manipulation in DVE 16.